The invention relates to computer-implemented methods for designing and maintaining networks.
Telecommunications networks have evolved into one of the most crucial elements of business and society. During the 1980's and 1990's major changes in network architectures have taken place. Data networks that were hierarchical in nature have moved to more distributed topologies. Voice, video, and data are now being combined into digital bit streams. The trend is for network services that are faster, cheaper, and open to wide ranges of services and information.
Local Area Networks (LANs) have become entrenched as the foundation for the new paradigm in corporate computing, known as Client-Server. For technical and economic reasons large users have generally moved away from large mainframe computers to higher-performance, lower-priced platforms. Standard desktop devices are now extremely powerful personal computers, connected to each other via LANs. The LANs are interconnected to form what is known as an internetwork--the transport vehicle for wide ranges of applications. The LANs and/or the internetwork may also be connectable to the Internet.
The internetwork is a mixture of hardware and software technologies. The hardware includes things such as routers, hubs, LAN adapters, digital and analog circuits, multiplexers, and switches of many varieties as well as desktop workstations and servers. Elements are combined into networks that extend from a single workgroup, floor, or building, to campuswide, metropolitan, and nationwide areas. Internetworking software includes elements such as protocol stacks (such as TCP/IP), device drivers, operating systems, and applications. When an internetwork infrastructure is assembled correctly it can create a computing environment which--while dauntingly complex--is nevertheless extremely powerful, and can be considered among a corporation's most valuable assets.
Mission-critical applications depend on this complex internetwork--from off-the-shelf solutions like electronic mail and file sharing, to complex database inquiry and transaction-processing systems. Development continues in the areas of client-server and multimedia applications. In addition, the "Information Highway" on the Internet is taking shape, and commercial internetworking is becoming available to everyone from multinational enterprises to smaller service-oriented businesses.
Distributed networks are composed of such a large number of elements that are both network-specific (routers, hubs, switches, facilities, etc.) and non-network-specific (servers, workstations, operating systems, application software, etc.) that just keeping track of where they are is a tough task, let alone how they interact as a system. In addition, each element has its own behavioral characteristics and likely comes from a different vendor. As systems made up of these elements experience change or encounter problems--congestion, circuit failure, or component degradation--overall effects can range from a minor slowdown to complete collapse.
While businesses are becoming increasingly dependent on internetworking, little attention has been paid to the process of correctly designing and implementing these networks. On one hand businesses pay dearly for high-priced hardware resellers and systems integrators to recommend vendor solutions--and on the other hand businesses that recognize the critical nature of these networks pay an even higher price for after-the-fact "network management" solutions from hardware system vendors. Despite the high price tag, however, most data engineering shops validate their network design by building the network, throwing real live users' traffic at it, and analyzing how well it runs.
In the Open System Interconnection (OSI) network architectural model, illustrated in FIG. 46, the network layer (Layer 3) deals with the transfer of data between devices on different networks. Thus, routing occurs at this layer. The network layer distinguishes itself from other layers in that it adds the concept of a network address, which is a specific identifier for each intermediate network between the data source and destination. This destination may require transfer across one or more gateways (typically routers) in a logically hierarchical network structure. Communications protocols, including the widely-used Internet Protocol (IP), have been established for relaying data across vast networks.